| 1. |
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| 2. |
- Feifel, Raimund, et al.
(author)
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Probing the valence character of O-1s -> Rydberg excited O-2 by participator Auger decay measurements and partial ion yield spectroscopy following x-ray absorption
- 2007
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In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 126:17, s. 174304-
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Journal article (peer-reviewed)abstract
- The valence character of O 1s -> Rydberg excited O-2 is investigated by means of participator Auger decay spectroscopy, performed at selected photon energies across the K-shell resonance region, and by means of partial ion yield x-ray absorption spectroscopy. For several of the excitation energies studied, the authors find substantial sigma(*)((4)Sigma(-)(u),(2)Sigma(-)(u)) valence character being mixed with ns sigma and np sigma ((4)Sigma(-)(u),(2)Sigma(-)(u)) Rydberg states. An experimental indication of a coupling between the channels associated with quartet and doublet ion cores is considered and discussed. New spectroscopic constants are derived for the singly ionized X (2)Pi(g) state of O-2 based on the observation of at least 20 vibrational sublevels.
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| 3. |
- Gopakumar, Geethanjali, 1992-, et al.
(author)
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Probing Aqueous Ions with Non-local Auger Relaxation
- 2022
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In: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 24:15, s. 8661-8671
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Journal article (peer-reviewed)abstract
- The decay of core holes is often regarded as a local process, but in some systems, it involves the autoionization of neighbouring atoms or molecules. Here, we explore such non-local autoionization (Intermolecular Coulombic Decay, ICD) of surrounding molecules upon 1s ionization of aqueous-phase Na+, Mg2+ and Al3+ ions. The three ions are isoelectronic but differ in the strength of the ion-water interactions which is manifested in experimental Auger electron spectra by varying intensities. While for strongly interacting Mg2+ and Al3+ the non-local decay is observed, for weakly bound Na+ no signal was measured. Combined with theoretical simulations we provide a microscopic understanding of the non-local decay processes. We assigned the ICD to decay processes ending with two-hole states delocalized between the central ion and neighbouring water. The ICD process is also shown to be highly selective with respect to water molecular orbitals. The ICD lifetime was estimated to be around 40 fs for Mg and 20 fs for Al. Auger spectroscopy thus represents a novel tool for exploring molecules in the liquid phase, providing simultaneously structural and electronic information.
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| 4. |
- Gopakumar, G., et al.
(author)
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Radiation damage by extensive local water ionization from two-step electron-transfer-mediated decay of solvated ions
- 2023
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In: Nature Chemistry. - : Nature Publishing Group. - 1755-4330 .- 1755-4349. ; 15:10, s. 1408-1414
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Journal article (peer-reviewed)abstract
- Biomolecular radiation damage is largely mediated by radicals and low-energy electrons formed by water ionization rather than by direct ionization of biomolecules. It was speculated that such an extensive, localized water ionization can be caused by ultrafast processes following excitation by core-level ionization of hydrated metal ions. In this model, ions relax via a cascade of local Auger–Meitner and, importantly, non-local charge- and energy-transfer processes involving the water environment. Here, we experimentally and theoretically show that, for solvated paradigmatic intermediate-mass Al3+ ions, electronic relaxation involves two sequential solute–solvent electron transfer-mediated decay processes. The electron transfer-mediated decay steps correspond to sequential relaxation from Al5+ to Al3+ accompanied by formation of four ionized water molecules and two low-energy electrons. Such charge multiplication and the generated highly reactive species are expected to initiate cascades of radical reactions. [Figure not available: see fulltext.]
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| 5. |
- Lindblad, Andreas, et al.
(author)
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Chemical shifts of small heterogeneous Ar/Xe clusters
- 2011
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In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 83:12, s. 125414-
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Journal article (peer-reviewed)abstract
- Heterogeneous rare-gas clusters produced by a coexpansion of an argon/xenon mixture have been studied using synchrotron-radiation-based photoelectron spectroscopy. Both valence and Xe 4d(5/2) core-level photoelectron spectra were recorded for three different concentrations of the primary argon/xenon mixture and, for those mixtures, spectra were recorded at several different stagnation conditions. The studied size regime of the mixed clusters ranges from large, similar to those studied in an earlier paper [Phys. Rev. A 69, 031210(R) (2004)], to very small-as reflected in the cluster line shapes and chemical shifts. The chemical shifts obtained from a curve fitting procedure similar to that used in our earlier paper are discussed in terms of the mixed cluster structure which can be expected from equilibrium considerations and the Lennard-Jones parameters of the constituent atoms. Molecular dynamics simulations of the vertical polarization shifts allow more specific assignments of "on-top" sites and interfacial sites.
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| 6. |
- Lindblad, A, et al.
(author)
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Postcollision interaction in noble gas clusters: Observation of differences in surface and bulk line shapes
- 2005
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In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 123:21
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Journal article (peer-reviewed)abstract
- The surface and bulk components of the x-ray photoelectron spectra of free noble gas clusters are shown to display differences in the influence of postcollision interaction between the photoelectron and the Auger electron on the spectral line shape; the bulk component is observed to be less affected than the surface and atomic parts of the spectra. A model for postcollision interaction in nonmetallic solids and clusters is also provided which takes the polarization screening into account. Core-level photoelectron spectra of Ar, Kr, and Xe have been recorded to verify the dependence of the postcollision interaction effect on the polarizability of the sample.
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| 7. |
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| 8. |
- Lundwall, Marcus, et al.
(author)
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Self-assembled heterogeneous argon/neon core-shell clusters studied by photoelectron spectroscopy
- 2007
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In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 126:21, s. 214706-
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Journal article (peer-reviewed)abstract
- Clusters formed by a coexpansion process of argon and neon have been studied using synchrotron radiation. Electrons from interatomic Coulombic decay as well as ultraviolet and x-ray photoelectron spectroscopy were used to determine the heterogeneous nature of the clusters and the cluster structure. Binary clusters of argon and neon produced by coexpansion are shown to exhibit a core-shell structure placing argon in the core and neon in the outer shells. Furthermore, the authors show that 2 ML of neon on the argon core is sufficient for neon valence band formation resembling the neon solid. For 1 ML of neon the authors observe a bandwidth narrowing to about half of the bulk value.
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| 9. |
- Mucke, Melanie, et al.
(author)
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Competition of inelastic electron scattering and Interatomic Coulombic Decay in Ne clusters
- 2015
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In: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 200, s. 232-238
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Journal article (peer-reviewed)abstract
- The creation of slow electrons due to Interatomic Coulombic Decay of 2s vacancies in Ne clusters is quantitatively compared to the slow electron yield by intracluster electron impact ionization. Using electron-electron coincidence spectroscopy, both channels can be separated experimentally. Two cluster size distributions, corresponding to two and five to six filled solvation shells, are probed.
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| 10. |
- Mucke, Melanie, et al.
(author)
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Performance of a short "magnetic bottle" electron spectrometer
- 2012
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In: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 83:6
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Journal article (peer-reviewed)abstract
- In this article, a newly constructed electron spectrometer of the magnetic bottle type is described. The instrument is part of an apparatus for measuring the electron spectra of free clusters using synchrotron radiation. Argon and helium outer valence photoelectron spectra have been recorded in order to investigate the characteristic features of the spectrometer. The energy resolution (E/Delta E) has been found to be similar to 30. Using electrostatic retardation of the electrons, it can be increased to at least 110. The transmission as a function of kinetic energy is flat, and is not impaired much by retardation with up to 80% of the initial kinetic energy. We have measured a detection efficiency of most probably 0.6(-0.1)(+0.05), but at least of 0.4. Results from testing the alignment of the magnet, and from trajectory simulations, are also discussed. [http://dx.doi.org/10.1063/1.4729256]
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